Starting from new experimental facts given by ESR, MS, and other physical and chemical methods, the role of bridged intermediates in the formation of catalytic active solids by thermal chemical reactions including the gaseous phase is discussed. Structures of oxygen-bridged adducts of AlF3 and AlCl3 with OH- and H2O have been explored at the HF and MP2 levels using 6-31G*, 6-31+G*, and 6-311G** basis sets, The reaction enthalpies of complex formation are calculated for several temperatures. Both hydroxyl and water complexes were found to be energetically stable complexes that have a real chance to take part in high-temperature heterogeneous reactions like the formation of activated aluminum halide catalysts.